Wearable cardioverter defibrillator (wcd) system computing heart rate from noisy ecg signal

ABSTRACT

In embodiments, a WCD system includes electrodes with which it senses an ECG signal of the patient. A processor may detect sequential peaks within the ECG signal, measure durations of time intervals between the peaks, including between non-sequential peaks, and identify a representative duration that best meets a plausibility criterion. The plausibility criterion may be that the representative duration is the one that occurs the most often, i.e. is the mode. Then a heart rate can be computed from a duration indicated by the representative duration and, if the heart rate meets a shock condition, the WCD system may deliver a shock to the patient. An advantage can be that the representative duration can be close to a good R-R interval measurement of a patient, notwithstanding noise in the ECG signal that is in the shape of peaks.

CROSS REFERENCE TO RELATED PATENT APPLICATIONS

The present application is a continuation of U.S. application Ser. No.15/948,884 filed Apr. 9, 2018, which is a continuation-in-part of U.S.application Ser. No. 15/880,853 filed Jan. 26, 2018. Said applicationSer. No. 15/948,884 and said application Ser. No. 15/880,853 both claimthe benefit of U.S. Provisional Application No. 62/501,009 filed on May3, 2017. Said application Ser. No. 15/948,884, said application Ser. No.15/880,853, and said Application No. 62/501,009 are hereby incorporatedherein by reference in their entireties.

BACKGROUND

When people suffer from some types of heart arrhythmias, the result maybe that blood flow to various parts of the body is reduced. Somearrhythmias may even result in a Sudden Cardiac Arrest (SCA). SCA canlead to death very quickly, e.g. within 10 minutes, unless treated inthe interim.

Some people have an increased risk of SCA. People at a higher riskinclude patients who have had a heart attack, or a prior SCA episode. Afrequent recommendation is for these people to receive an ImplantableCardioverter Defibrillator (ICD). The ICD is surgically implanted in thechest, and continuously monitors the patient's electrocardiogram (ECG).If certain types of heart arrhythmias are detected, then the ICDdelivers an electric shock through the heart.

After being identified as having an increased risk of an SCA, and beforereceiving an ICD, these people are sometimes given a WearableCardioverter Defibrillator (WCD) system. (Early versions of such systemswere called wearable cardiac defibrillator systems.) A WCD systemtypically includes a harness, vest, or other garment that the patient isto wear. The WCD system further includes electronic components, such asa defibrillator and electrodes, coupled to the harness, vest, or othergarment. When the patient wears the WCD system, the external electrodesmay then make good electrical contact with the patient's skin, andtherefore can help sense the patient's ECG. If a shockable heartarrhythmia is detected, then the defibrillator delivers the appropriateelectric shock through the patient's body, and thus through the heart.

A challenge in the prior art is that the patient's ECG signal may becorrupted by electrical noise. As such, it can be hard to interpret theECG signal.

All subject matter discussed in this Background section of this documentis not necessarily prior art, and may not be presumed to be prior artsimply because it is presented in this Background section. Plus, anyreference to any prior art in this description is not, and should not betaken as, an acknowledgement or any form of suggestion that such priorart forms parts of the common general knowledge in any art in anycountry. Along these lines, any recognition of problems in the prior artdiscussed in this Background section or associated with such subjectmatter should not be treated as prior art, unless expressly stated to beprior art. Rather, the discussion of any subject matter in thisBackground section should be treated as part of the approach takentowards the particular problem by the inventor. This approach in and ofitself may also be inventive.

BRIEF SUMMARY

The present description gives instances of wearable cardioverterdefibrillator (WCD) systems, storage media that store programs, andmethods, the use of which may help overcome problems and limitations ofthe prior art.

In embodiments, a WCD system includes electrodes with which it senses anECG signal of the patient. A processor may detect sequential peakswithin the ECG signal, measure durations of time intervals between thepeaks, including between non-sequential peaks, and identify arepresentative duration that best meets a plausibility criterion. Theplausibility criterion may be that the representative duration is theone that occurs the most often, i.e. is the mode. Then a heart rate canbe computed from a duration indicated by the representative durationand, if the heart rate meets a shock condition, the WCD system maydeliver a shock to the patient.

An advantage can be that the representative duration can be close to agood R-R interval measurement of a patient, notwithstanding noise in theECG signal that is in the shape of peaks.

These and other features and advantages of the claimed invention willbecome more readily apparent in view of the embodiments described andillustrated in this specification, namely from this writtenspecification and the associated drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of components of a sample wearable cardioverterdefibrillator (WCD) system, made according to embodiments.

FIG. 2 is a diagram showing sample components of an externaldefibrillator, such as the one belonging in the system of FIG. 1 , andwhich is made according to embodiments.

FIG. 3A is a conceptual diagram for illustrating how differentelectrodes may sense ECG signals of the patient along different vectorsaccording to embodiments.

FIG. 3B is a conceptual diagram for illustrating how a first ECG signalmay be used for in a heart rate computation while a second sense ECGsignal of the patient may be used for a shock decision according toembodiments.

FIG. 4 shows time diagrams for illustrating how a patient's heart ratemay be detected from a noise-free ECG signal in the prior art.

FIG. 5 is a time diagram for showing how noise in an ECG signal cancorrupt the measurements used for the heart rate detection of FIG. 4 .

FIG. 6 is a time diagram for showing how a patient's heart rate may bedetected from a noisy ECG signal according to embodiments.

FIG. 7 is a time diagram for showing how a patient's heart rate may bedetected from a noisy ECG signal, according to embodiments where allpossible peak pairs are established.

FIG. 8 is a bar chart for identifying which one of time durationsmeasured in FIG. 7 best meets a plausibility criterion, according toembodiments.

FIG. 9 is a bar chart of time durations measured in numbers of samplesaccording to embodiments.

FIG. 10 is the bar chart of FIG. 9 , where clusters of time durationshave been further discerned, according to embodiments.

FIG. 11 is a bar chart of time durations where clusters have beendiscerned, and further where fractional harmonics have been accountedfor, according to embodiments.

FIG. 12 is a flowchart for illustrating methods according toembodiments.

DETAILED DESCRIPTION

As has been mentioned, the present description is about wearablecardioverter defibrillator (WCD) systems, and related storage media,programs and methods. Embodiments are now described in more detail.

A wearable cardioverter defibrillator (WCD) system made according toembodiments has a number of components. These components can be providedseparately as modules that can be interconnected, or can be combinedwith other components, etc.

FIG. 1 depicts a patient 82. Patient 82 may also be referred to as aperson and/or wearer, since the patient is wearing components of the WCDsystem. Patient 82 is ambulatory, which means patient 82 can walkaround, and is not necessarily bed-ridden.

FIG. 1 also depicts components of a WCD system made according toembodiments. One such component is a support structure 170 that iswearable by patient 82. It will be understood that support structure 170is shown only generically in FIG. 1 , and in fact partly conceptually.FIG. 1 is provided merely to illustrate concepts about support structure170, and is not to be construed as limiting how support structure 170 isimplemented, or how it is worn.

Support structure 170 can be implemented in many different ways. Forexample, it can be implemented in a single component or a combination ofmultiple components. In embodiments, support structure 170 could includea vest, a half-vest, a garment, etc. In such embodiments such items canbe worn similarly to parallel articles of clothing. In embodiments,support structure 170 could include a harness, one or more belts orstraps, etc. In such embodiments, such items can be worn by the patientaround the torso, hips, over the shoulder, etc. In embodiments, supportstructure 170 can include a container or housing, which can even bewaterproof. In such embodiments, the support structure can be worn bybeing attached to the patient by adhesive material, for example as shownin U.S. Pat. No. 8,024,037. Support structure 170 can even beimplemented as described for the support structure of US Pat. App. No.US2017/0056682, which is incorporated herein by reference. Of course, insuch embodiments, the person skilled in the art will recognize thatadditional components of the WCD system can be in the housing of asupport structure instead of being attached externally to the supportstructure, for example as described in the US2017/0056682 document.There can be other examples.

A WCD system according to embodiments is configured to defibrillate apatient who is wearing it, by delivering an electrical charge to thepatient's body in the form of an electric shock delivered in one or morepulses. FIG. 1 shows a sample external defibrillator 100, and sampledefibrillation electrodes 104, 108, which are coupled to externaldefibrillator 100 via electrode leads 105. Defibrillator 100 anddefibrillation electrodes 104, 108 can be coupled to support structure170. As such, many of the components of defibrillator 100 could betherefore coupled to support structure 170. When defibrillationelectrodes 104, 108 make good electrical contact with the body ofpatient 82, defibrillator 100 can administer, via electrodes 104, 108, abrief, strong electric pulse 111 through the body. Pulse 111 is alsoknown as shock, defibrillation shock, therapy and therapy shock. Pulse111 is intended to go through and restart heart 85, in an effort to savethe life of patient 82. Pulse 111 can further include one or more pacingpulses, and so on.

A prior art defibrillator typically decides whether to defibrillate ornot based on an ECG signal of the patient. However, externaldefibrillator 100 may initiate defibrillation (or hold-offdefibrillation) based on a variety of inputs, with ECG merely being oneof them.

Accordingly, it will be appreciated that signals such as physiologicalsignals containing physiological data can be obtained from patient 82.While the patient may be considered also a “user” of the WCD system,this is not a requirement. That is, for example, a user of the wearablecardioverter defibrillator (WCD) may include a clinician such as adoctor, nurse, emergency medical technician (EMT) or other similarlysituated individual (or group of individuals). The particular context ofthese and other related terms within this description should beinterpreted accordingly.

The WCD system may optionally include an outside monitoring device 180.Device 180 is called an “outside” device because it could be provided asa standalone device, for example not within the housing of defibrillator100. Device 180 can be configured to sense or monitor at least one localparameter. A local parameter can be a parameter of patient 82, or aparameter of the WCD system, or a parameter of the environment, as willbe described later in this document. Device 180 may include one or moretransducers or sensors that are configured to render one or morephysiological inputs or signals from one or more patient parameters thatthey sense.

Optionally, device 180 is physically coupled to support structure 170.In addition, device 180 can be communicatively coupled with othercomponents, which are coupled to support structure 170. Suchcommunication can be implemented by a communication module, as will bedeemed applicable by a person skilled in the art in view of thisdescription.

FIG. 2 is a diagram showing components of an external defibrillator 200,made according to embodiments. These components can be, for example,included in external defibrillator 100 of FIG. 1 . The components shownin FIG. 2 can be provided in a housing 201, which may also be referredto as casing 201.

External defibrillator 200 is intended for a patient who would bewearing it, such as patient 82 of FIG. 1 . Defibrillator 200 may furtherinclude a user interface 280 for a user 282. User 282 can be patient 82,also known as wearer 82. Or, user 282 can be a local rescuer at thescene, such as a bystander who might offer assistance, or a trainedperson. Or, user 282 might be a remotely located trained caregiver incommunication with the WCD system.

User interface 280 can be made in a number of ways. User interface 280may include output devices, which can be visual, audible or tactile, forcommunicating to a user by outputting images, sounds or vibrations.Images, sounds, vibrations, and anything that can be perceived by user282 can also be called human-perceptible indications. There are manyexamples of output devices. For example, an output device can be alight, or a screen to display what is sensed, detected and/or measured,and provide visual feedback to rescuer 282 for their resuscitationattempts, and so on. Another output device can be a speaker, which canbe configured to issue voice prompts, beeps, loud alarm sounds and/orwords to warn bystanders, etc.

User interface 280 may further include input devices for receivinginputs from users. Such input devices may additionally include variouscontrols, such as pushbuttons, keyboards, touchscreens, one or moremicrophones, and so on. An input device can be a cancel switch, which issometimes called an “I am alive” switch or “live man” switch. In someembodiments, actuating the cancel switch can prevent the impendingdelivery of a shock.

Defibrillator 200 may include an internal monitoring device 281. Device281 is called an “internal” device because it is incorporated withinhousing 201. Monitoring device 281 can sense or monitor patientparameters such as patient physiological parameters, system parametersand/or environmental parameters, all of which can be called patientdata. In other words, internal monitoring device 281 can becomplementary or an alternative to outside monitoring device 180 of FIG.1 . Allocating which of the parameters are to be monitored by which ofmonitoring devices 180, 281 can be done according to designconsiderations. Device 281 may include one or more transducers orsensors that are configured to render one or more physiological inputsfrom one or more patient parameters that it senses.

Patient parameters may include patient physiological parameters. Patientphysiological parameters may include, for example and withoutlimitation, those physiological parameters that can be of any help indetecting by the wearable defibrillation system whether the patient isin need of a shock, plus optionally their medical history and/or eventhistory. Examples of such parameters include the patient's ECG, bloodoxygen level, blood flow, blood pressure, blood perfusion, pulsatilechange in light transmission or reflection properties of perfusedtissue, heart sounds, heart wall motion, breathing sounds and pulse.Accordingly, monitoring devices 180, 281 may include one or more sensorsconfigured to acquire patient physiological signals. Examples of suchsensors or transducers include electrodes to detect ECG data, aperfusion sensor, a pulse oximeter, a device for detecting blood flow(e.g. a Doppler device), a sensor for detecting blood pressure (e.g. acuff), an optical sensor, illumination detectors and sensors perhapsworking together with light sources for detecting color change intissue, a motion sensor, a device that can detect heart wall movement, asound sensor, a device with a microphone, an SpO₂ sensor, and so on. Inview of this disclosure, it will be appreciated that such sensors canhelp detect the patient's pulse, and can therefore also be called pulsedetection sensors, pulse sensors, and pulse rate sensors. Pulsedetection is also taught at least in Physio-Control's U.S. Pat. No.8,135,462, which is hereby incorporated by reference in its entirety. Inaddition, a person skilled in the art may implement other ways ofperforming pulse detection. In such cases, the transducer includes anappropriate sensor, and the physiological input is a measurement by thesensor of that patient parameter. For example, the appropriate sensorfor a heart sound may include a microphone, etc.

In some embodiments, the local parameter is a trend that can be detectedin a monitored physiological parameter of patient 282. A trend can bedetected by comparing values of parameters at different times.Parameters whose detected trends can particularly help a cardiacrehabilitation program include: a) cardiac function (e.g. ejectionfraction, stroke volume, cardiac output, etc.); b) heart ratevariability at rest or during exercise; c) heart rate profile duringexercise and measurement of activity vigor, such as from the profile ofan accelerometer signal and informed from adaptive rate pacemakertechnology; d) heart rate trending; e) perfusion, such as from SpO₂ orCO₂; f) respiratory function, respiratory rate, etc.; g) motion, levelof activity; and so on. Once a trend is detected, it can be storedand/or reported via a communication link, along perhaps with a warning.From the report, a physician monitoring the progress of patient 282 willknow about a condition that is either not improving or deteriorating.

Patient state parameters include recorded aspects of patient 282, suchas motion, posture, whether they have spoken recently plus maybe alsowhat they said, and so on, plus optionally the history of theseparameters. Or, one of these monitoring devices could include a locationsensor such as a Global Positioning System (GPS) location sensor. Such asensor can detect the location, plus a speed can be detected as a rateof change of location over time. Many motion detectors output a motionsignal that is indicative of the motion of the detector, and thus of thepatient's body. Patient state parameters can be very helpful innarrowing down the determination of whether SCA is indeed taking place.

A WCD system made according to embodiments may include a motiondetector. In embodiments, a motion detector can be implemented withinmonitoring device 180 or monitoring device 281. Such a motion detectorcan be made in many ways as is known in the art, for example by using anaccelerometer. In this example, a motion detector 287 is implementedwithin monitoring device 281.

A motion detector of a WCD system according to embodiments can beconfigured to detect a motion event. In response, the motion detectormay render or generate, from the detected motion event or motion, amotion detection input that can be received by a subsequent device orfunctionality. A motion event can be defined as is convenient, forexample a change in motion from a baseline motion or rest, etc. In suchcases, a sensed patient parameter is motion.

System parameters of a WCD system can include system identification,battery status, system date and time, reports of self-testing, recordsof data entered, records of episodes and intervention, and so on.

Environmental parameters can include ambient temperature and pressure.Moreover, a humidity sensor may provide information as to whether it islikely raining. Presumed patient location could also be considered anenvironmental parameter. The patient location could be presumed, ifmonitoring device 180 or 281 includes a GPS location sensor as per theabove, and if it is presumed that the patient is wearing the WCD system.

Defibrillator 200 typically includes a defibrillation port 210, such asa socket in housing 201. Defibrillation port 210 includes electricalnodes 214, 218. Leads of defibrillation electrodes 204, 208, such asleads 105 of FIG. 1 , can be plugged into defibrillation port 210, so asto make electrical contact with nodes 214, 218, respectively. It is alsopossible that defibrillation electrodes 204, 208 are connectedcontinuously to defibrillation port 210, instead. Either way,defibrillation port 210 can be used for guiding, via electrodes, to thewearer the electrical charge that has been stored in an energy storagemodule 250 that is described more fully later in this document. Theelectric charge will be the shock for defibrillation, pacing, and so on.

Defibrillator 200 may optionally also have a sensor port 219 in housing201, which is also sometimes known as an ECG port. Sensor port 219 canbe adapted for plugging in sensing electrodes 209, which are also knownas ECG electrodes and ECG leads. It is also possible that sensingelectrodes 209 can be connected continuously to sensor port 219,instead. Sensing electrodes 209 are types of transducers that can helpsense an ECG signal, e.g. a 12-lead signal, or a signal from a differentnumber of leads, especially if they make good electrical contact withthe body of the patient and in particular with the skin of the patient.Sensing electrodes 209 can be attached to the inside of supportstructure 170 for making good electrical contact with the patient,similarly with defibrillation electrodes 204, 208.

Optionally a WCD system according to embodiments also includes a fluidthat it can deploy automatically between the electrodes and thepatient's skin. The fluid can be conductive, such as by including anelectrolyte, for establishing a better electrical contact between theelectrode and the skin. Electrically speaking, when the fluid isdeployed, the electrical impedance between the electrode and the skin isreduced. Mechanically speaking, the fluid may be in the form of alow-viscosity gel, so that it does not flow away from the electrode,after it has been deployed. The fluid can be used for bothdefibrillation electrodes 204, 208, and for sensing electrodes 209.

The fluid may be initially stored in a fluid reservoir, not shown inFIG. 2 , which can be coupled to the support structure. In addition, aWCD system according to embodiments further includes a fluid deployingmechanism 274. Fluid deploying mechanism 274 can be configured to causeat least some of the fluid to be released from the reservoir, and bedeployed near one or both of the patient locations, to which theelectrodes are configured to be attached to the patient. In someembodiments, fluid deploying mechanism 274 is activated prior to theelectrical discharge responsive to receiving activation signal AS from aprocessor 230, which is described more fully later in this document.

FIG. 3A is a conceptual diagram for illustrating how electrodes of a WCDsystem may sense or capture ECG signals along different vectorsaccording to embodiments. A section of a patient 382 having a heart 385is shown. There are four electrodes 304, 306, 307, 308, attached to thetorso of patient 382, each with a wire lead 305. Any pair of theseelectrodes defines a vector, across which an ECG signal may be measured.These vectors are also known as channels and ECG channels. The fourelectrodes 304, 306, 307, 308 therefore can define six vectors, acrosswhich six respective ECG signals 311, 312, 313, 314, 315, 316 can besensed. FIG. 3A thus illustrates a multi-vector situation. In FIG. 3A itwill be understood that electrodes 304, 306, 307, 308 are drawn on thesame plane for simplicity, while that is not necessarily the case.Accordingly, the vectors of ECG signals 311-316 are not necessarily onthe same plane, either.

Any one of ECG signals 311-316 might provide sufficient data for makinga shock/no shock determination. The effort is to shock when needed, andnot shock when not needed. The problem is that, at any given point intime, some of these ECG signals may include noise, while others not. Thenoise may be due to patient movement or how well the electrodes contactthe skin. The noise problem for a WCD may be further exacerbated by thedesire to use dry, non-adhesive monitoring electrodes. Dry, non-adhesiveelectrodes are thought to be more comfortable for the patient to wear inthe long term, but may produce more noise than a conventional ECGmonitoring electrode that includes adhesive to hold the electrode inplace and an electrolyte gel to reduce the impedance of theelectrode-skin interface.

FIG. 3A also shows a measurement circuit 320 and a processor 330, whichcan be made as described for measurement circuit 220 and processor 230later in this document. Processor 330 may further compute a heart rate333 according to embodiments, as described in more detail further inthis document.

Returning to FIG. 2 , defibrillator 200 also includes a measurementcircuit 220, as one or more of its sensors or transducers. Measurementcircuit 220 senses one or more electrical physiological signals of thepatient from sensor port 219, if provided. Even if defibrillator 200lacks sensor port 219, measurement circuit 220 may optionally obtainphysiological signals through nodes 214, 218 instead, whendefibrillation electrodes 204, 208 are attached to the patient. In thesecases, the physiological input reflects an ECG measurement. The patientparameter can be an ECG, which can be sensed as a voltage differencebetween electrodes 204, 208. In addition the patient parameter can be animpedance, which can be sensed between electrodes 204, 208 and/or theconnections of sensor port 219. Sensing the impedance can be useful fordetecting, among other things, whether these electrodes 204, 208 and/orsensing electrodes 209 are not making good electrical contact with thepatient's body. These patient physiological signals can be sensed, whenavailable. Measurement circuit 220 can then render or generateinformation about them as physiological inputs, data, other signals,etc. More strictly speaking, the information rendered by measurementcircuit 220 is output from it, but this information can be called aninput because it is received by a subsequent device or functionality asan input.

Defibrillator 200 also includes a processor 230. Processor 230 may beimplemented in a number of ways. Such ways include, by way of exampleand not of limitation, digital and/or analog processors such asmicroprocessors and Digital Signal Processors (DSPs); controllers suchas microcontrollers; software running in a machine; programmablecircuits such as Field Programmable Gate Arrays (FPGAs),Field-Programmable Analog Arrays (FPAAs), Programmable Logic Devices(PLDs), Application Specific Integrated Circuits (ASICs), anycombination of one or more of these, and so on.

Processor 230 may include, or have access to, a non-transitory storagemedium, such as memory 238 that is described more fully later in thisdocument. Such a memory can have a non-volatile component for storage ofmachine-readable and machine-executable instructions. A set of suchinstructions can also be called a program. The instructions, which mayalso be referred to as “software,” generally provide functionality byperforming methods as may be disclosed herein or understood by oneskilled in the art in view of the disclosed embodiments. In someembodiments, and as a matter of convention used herein, instances of thesoftware may be referred to as a “module” and by other similar terms.Generally, a module includes a set of the instructions so as to offer orfulfill a particular functionality. Embodiments of modules and thefunctionality delivered are not limited by the embodiments described inthis document.

Processor 230 can be considered to have a number of modules. One suchmodule can be a detection module 232. Detection module 232 can include aVentricular Fibrillation (VF) detector. The patient's sensed ECG frommeasurement circuit 220, which can be available as physiological inputs,data, or other signals, may be used by the VF detector to determinewhether the patient is experiencing VF. Detecting VF is useful, becauseVF typically results in SCA. Detection module 232 can also include aVentricular Tachycardia (VT) detector, and so on.

Another such module in processor 230 can be an advice module 234, whichgenerates advice for what to do. The advice can be based on outputs ofdetection module 232. There can be many types of advice according toembodiments. In some embodiments, the advice is a shock/no shockdetermination that processor 230 can make, for example via advice module234. The shock/no shock determination can be made by executing a storedShock Advisory Algorithm. A Shock Advisory Algorithm can make a shock/noshock determination from one or more ECG signals that are sensed orcaptured according to embodiments, and determining whether a shockcriterion is met. The determination can be made from a rhythm analysisof the sensed or captured ECG signal or otherwise.

In some embodiments, when the determination is to shock, an electricalcharge is delivered to the patient. Delivering the electrical charge isalso known as discharging. Shocking can be for defibrillation, pacing,and so on.

Processor 230 can include additional modules, such as other module 236,for other functions. In addition, if internal monitoring device 281 isindeed provided, it may be operated in part by processor 230, etc.

Defibrillator 200 optionally further includes a memory 238, which canwork together with processor 230. Memory 238 may be implemented in anumber of ways. Such ways include, by way of example and not oflimitation, volatile memories, Nonvolatile Memories (NVM), Read-OnlyMemories (ROM), Random Access Memories (RAM), magnetic disk storagemedia, optical storage media, smart cards, flash memory devices, anycombination of these, and so on. Memory 238 is thus a non-transitorystorage medium. Memory 238, if provided, can include programs forprocessor 230, which processor 230 may be able to read and execute. Moreparticularly, the programs can include sets of instructions in the formof code, which processor 230 may be able to execute upon reading.Executing is performed by physical manipulations of physical quantities,and may result in functions, operations, processes, actions and/ormethods to be performed, and/or the processor to cause other devices orcomponents or blocks to perform such functions, operations, processes,actions and/or methods. The programs can be operational for the inherentneeds of processor 230, and can also include protocols and ways thatdecisions can be made by advice module 234. In addition, memory 238 canstore prompts for user 282, if this user is a local rescuer. Moreover,memory 238 can store data. This data can include patient data, systemdata and environmental data, for example as learned by internalmonitoring device 281 and outside monitoring device 180. The data can bestored in memory 238 before it is transmitted out of defibrillator 200,or stored there after it is received by defibrillator 200.

Defibrillator 200 may also include a power source 240. To enableportability of defibrillator 200, power source 240 typically includes abattery. Such a battery is typically implemented as a battery pack,which can be rechargeable or not. Sometimes a combination is used ofrechargeable and non-rechargeable battery packs. Other embodiments ofpower source 240 can include an AC power override, for where AC powerwill be available, an energy-storing capacitor, and so on. In someembodiments, power source 240 is controlled by processor 230.Appropriate components may be included to provide for charging orreplacing power source 240.

Defibrillator 200 may additionally include an energy storage module 250.Energy storage module 250 can be coupled to the support structure of theWCD system, for example either directly or via the electrodes and theirleads. Module 250 is where some electrical energy can be storedtemporarily in the form of an electrical charge, when preparing it fordischarge to administer a shock. In embodiments, module 250 can becharged from power source 240 to the desired amount of energy, ascontrolled by processor 230. In typical implementations, module 250includes a capacitor 252, which can be a single capacitor or a system ofcapacitors, and so on. In some embodiments, energy storage module 250includes a device that exhibits high power density, such as anultracapacitor. As described above, capacitor 252 can store the energyin the form of an electrical charge, for delivering to the patient.

Defibrillator 200 moreover includes a discharge circuit 255. When thedecision is to shock, processor 230 can be configured to controldischarge circuit 255 to discharge through the patient the electricalcharge stored in energy storage module 250. When so controlled, circuit255 can permit the energy stored in module 250 to be discharged to nodes214, 218, and from there also to defibrillation electrodes 204, 208, soas to cause a shock to be delivered to the patient. Circuit 255 caninclude one or more switches 257. Switches 257 can be made in a numberof ways, such as by an H-bridge, and so on. Circuit 255 can also becontrolled via user interface 280.

Defibrillator 200 can optionally include a communication module 290, forestablishing one or more wired or wireless communication links withother devices of other entities, such as a remote assistance center,Emergency Medical Services (EMS), and so on. The data can includepatient data, event information, therapy attempted, CPR performance,system data, environmental data, and so on. For example, communicationmodule 290 may transmit wirelessly, e.g., on a daily basis, heart rate,respiratory rate, and other vital signs data to a server accessible overthe internet, for instance as described in US 20140043149. This data canbe analyzed directly by the patient's physician and can also be analyzedautomatically by algorithms designed to detect a developing illness andthen notify medical personnel via text, email, phone, etc. Module 290may also include such interconnected sub-components as may be deemednecessary by a person skilled in the art, for example an antenna,portions of a processor, supporting electronics, outlet for a telephoneor a network cable, etc. This way, data, commands, etc. can becommunicated.

Defibrillator 200 can optionally include other components.

Returning to FIG. 1 , in embodiments, one or more of the components ofthe shown WCD system have been customized for patient 82. Thiscustomization may include a number of aspects. For instance, supportstructure 170 can be fitted to the body of patient 82. For anotherinstance, baseline physiological parameters of patient 82 can bemeasured, such as the heart rate of patient 82 while resting, whilewalking, motion detector outputs while walking, etc. Such baselinephysiological parameters can be used to customize the WCD system, inorder to make its diagnoses more accurate, since the patients' bodiesdiffer from one another. Of course, such parameters can be stored in amemory of the WCD system, and so on.

A programming interface can be made according to embodiments, whichreceives such measured baseline physiological parameters. Such aprogramming interface may input automatically in the WCD system thebaseline physiological parameters, along with other data.

Detection of the heart rate from the ECG signal is now described in moredetail.

FIG. 3B is a conceptual diagram that includes a time axis 348. A firstsample ECG signal 317 and a second sample ECG signal 318 of the patientare shown with reference to time axis 348. Second ECG signal 318 hasbeen sensed after sensing first ECG signal 317. It will be recognizedthat sample ECG signals 317, 318 indicate VT, but that is only forexample. Either one of ECG signals 317, 318 may be sensed from any ofthe ECG channels or vectors of FIG. 3A, regardless of the fact that theyare shown against the same time axis 348.

First ECG signal 317 may result in computing heart rate 333 according toembodiments. The computing heart rate 333 may be stored in memory 238,which is repeated in FIG. 3B. The heart rate stored in memory 238 maythen be downloaded later, transmitted wirelessly via communicationmodule 290, displayed by a screen of user interface 280, and so on.

Second ECG signal 318 may be used to determine whether or not a shockcriterion is met, for example by advice module 234. Second ECG signal318 may or may not have been used to compute the heart rate according toembodiments.

If so, processor 230 may control, responsive to the shock criterionbeing met, discharge circuit 255 to discharge through patient 82electrical charge that is stored in energy storage module 250, whilesupport structure 170 is worn by patient 82 so as to deliver a shock 111to 82 patient.

FIG. 4 shows an ECG signal in a time diagram 409. Diagram 409 has an ECGamplitude axis 407 and a time axis 408. Diagram 409 depicts asomewhat-idealized, noise-free ECG signal of patient 82, as it might besensed from a single channel 311. The ECG signal of diagram 409 hoversaround a horizontal baseline value BL. Baseline value BL can beconsidered to be zero, or it might be changing value due to noise, asdescribed later in this document.

The ECG signal of diagram 409 includes three full heartbeats. Inparticular, three peaks 421, 422, 423 are shown, which occursequentially. It will be recognized that peaks 421, 422, 423 are due toQRS complexes, each of which is followed by a T-wave of lesseramplitude. In this somewhat-idealized signal, a P-wave before the QRScomplex and a U-wave after the QRS complex are not shown at all. The ECGsignal of diagram 409 is further idealized in that the QRS complexes areshown as peaks, or spikes; in fact, some heart rhythms have QRScomplexes that don't look like spikes.

Peaks 421, 422, 423 are typically used for detecting the heart rate,because their large amplitude relative to the remainder of the ECGsignal makes them easier to identify and/or detect. In particular, FIG.4 also shows another time axis 448. Time axis 448 indicates only thetime occurrences 441, 442, 443 of peaks 421, 422, 423, respectively.Moreover, the successive peaks are considered in pairs to define timeintervals. In particular, the pair of peaks 421 and 422 defines a timeinterval 451 from time occurrences 441, 442, while the pair of peaks 422and 423 defines a time interval 452 from time occurrences 442, 443. Timeintervals 451, 452 are sometimes called R-R intervals of the ECG signal.The durations of time intervals 451, 452 are measured, and heart rate333 of the patient is thus computed from them.

It will be recognized that this process of computing heart rate 333 frompeaks 421, 422, 423 in the ECG signal is the same regardless of howthese peaks 421, 422, 423 are detected. Medical devices sometimesmeasure the ECG signal electronically and focus on these peaks to detectthe R-R interval, for example as per the above. Other times, peaks 421,422, 423 correspond with peaks in the patient's blood pressure, whichcan be sensed by someone placing their hand against the neck or a wristof a patient.

It is more difficult, however, to measure the patient's heart rate fromthese peaks in the presence of noise in the ECG signal. An example isnow described.

FIG. 5 shows an ECG signal in a time diagram 529. Diagram 529 has an ECGpeaks axis 527 and a time axis 528. Diagram 529 depicts only peaks 521,522, 523, 524, 525 of an ECG signal, with all other values of the ECGsignal being shown as zero for simplification. This simplification isacceptable in this instance, as FIG. 5 is used for discussing only thedetection of the heart rate, and only by the peaks of the ECG signal.

FIG. 5 also shows a time diagram 539 to depict sample noise that couldbe added to the ECG of diagram 529. Diagram 539 has a Noise peaks axis537 and a time axis 538. Diagram 539 depicts only peaks 531, 532 ofnoise, with all other values of the sample noise being shown as zero forsimplification. In addition, noise peaks 531, 532 may have unequalamplitudes.

FIG. 5 further shows another time axis 548. Time axis 548 indicates onlythe time occurrences 541, 542, 543, 544, 545, 546, 547 of peaks 521-525and also of peaks 531, 532. Time intervals 551, 552, 553, 554, 555, 556can be used to compute a heart rate 533. It is clear, however, thatthese time intervals 551-556 are no longer true R-R intervals, as theywere in the idealized noise-free case of FIG. 4 , because of the noisein the ECG signal. As such, computed heart rate 533 may not be the trueheart rate 333. Rather, in the situation of FIG. 5 , the patient may bemisdiagnosed with tachycardia due to noise peaks 531, 532.

In embodiments, however, the true heart rate 333 is measured, even inthe presence of noise. Examples are now described.

Referring now to FIG. 6 , a time diagram 609 has an ECG amplitude axis607 and a time axis 608. Diagram 609 depicts an actual ECG signal of apatient. This ECG signal hovers around a horizontal baseline value BL.The units of time axis shows the ordinal number of a sample, i.e.200^(th), 400^(th), etc.

In embodiments, peaks are detected, which occur sequentially within asensed ECG signal. In the example of FIG. 6 , peaks 621, 622, 623, 624,625, 626, 627, 628, 629 are detected, which occur sequentially. Thesepeaks are detected in an effort to identify QRS complexes such as thoseof FIG. 4 , with the apprehension that some of these peaks may be due tonoise as seen in FIG. 5 .

For purposes of detection, a number of criteria can be advantageouslyapplied. For example, all peaks could have the same polarity, as QRScomplexes do. Peaks of the opposite polarity can be ignored. In thisexample the polarity is positive, but it could equivalently be negative.Moreover, a peak can be deemed detected if it meets certain criteria,such as amplitude (e.g., relatively large rise over previous values, andrelatively large fall back to about the same values), sharpness (e.g.,relatively steep rise and relatively steep fall), and width (e.g., notwider beyond a threshold at mid-amplitude).

FIG. 6 also shows another time axis 648. Time axis 648 indicates onlythe time occurrences 641, 642, 643, 644, 645, 646, 647 of detected peaks621, 622, 623, 624, 625, 626, 627 respectively.

In embodiments, pairs of the detected peaks can be established, where atleast one of the pairs is established by peaks that do not occursequentially. Such pairs may thus define time intervals. Then durationsof the time intervals can be measured. In the example of FIG. 6 , a pairof peaks 621 & 622 defines a time interval 651 between time occurrences641 & 642. The same is true for time intervals 652 and 654, and so on.

It will be noted that a pair of peaks 621 & 623 define a time interval653 between time occurrences 641 & 643. In this case, however, peaks 621& 623 do not occur sequentially; rather, peak 622 occurs after peak 621and before peak 623. And it will be recognized that, absent any noiseand assuming perfect detection, time interval 653 will be a lot largerthan either time interval 651 or 652. In fact, the duration of timeinterval 653 would be the sum of the durations of time intervals 651 and652. Similarly, a pair of peaks 621 & 624, which do not occursequentially, define a time interval 655 between time occurrences 641 &644, and so on. More durations could be shown in FIG. 6 .

In embodiments, these durations 651, 652, 653, 654, 655 can be used tocompute heart rate 333 as further described later in this document.

In some embodiments, pairs are established among only some of thedetected peaks. This can be implemented from the beginning, for exampleby not establishing all the possible pairs in FIG. 6 . This can beimplemented after some of the processing described later where all thepossible pairs are established. At that time which a recognition valuemay be computed. Then a peak may be rejected, at least tentatively, forexample according to a recognition criterion. It may turn out thatrejecting the peak improves the recognition value, and detection ofheart rate 333 becomes more robust.

In some embodiments, all possible pairs of the detected peaks areestablished. An example is now described.

FIG. 7 shows a time axis 748. Time axis 748 indicates only the timeoccurrences 741, 742, 743, 744, 745, 746 of peaks detected as describedelsewhere in this document. For this discussion, pairs of peaks may bereferred to by the time durations they define. For example, peaks at 741& 742 define a time duration 751. In turn, time duration 751 has aduration indicated by arrow 761. In this example, time duration 751 hasa measured duration of 5. Of course, this value of 5 can be in relativeterms for this example.

It will be recognized that the peak at 741 defines a group 771 of timeoccurrences with each of the remaining considered peaks. Similarly, thepeak at 742 defines a group 772 of time occurrences with each of theremaining considered peaks, and so on with groups 773, 774, and singletime occurrence 755. As such, group 777 is a group of all possible pairsof peaks 741, 742, 743, 744, 745, 746. Each pair is shown by an arrow,with its measured duration as a number within the arrow.

In some embodiments, it can be identified which one of the measureddurations occurs the most often. The heart rate of the patient can becomputed from the identified duration. An example is now described.

FIG. 8 is a bar chart 806. Its horizontal axis 802 shows possible valuesfor the measured durations of time intervals. Its vertical axis 804shows numbers for how often a measured interval had the duration ofhorizontal axis 802. As such, bar chart 806 is not a time diagram.

Time durations 777 have been plotted in bar chart 806. As such, the timeintervals defined by the peak pairs have been classified by theirdurations.

A salient feature of bar chart 806 is bar 881, which is the tallest. Assuch, it can be identified that the measured duration that occurs themost often has a duration of 5. Other features are bars 882, 883, 884,which occur at durations of 10, 15 and 20, and are the 2^(nd), 3^(rd),and 4^(th) harmonics of bar 881.

Bars 889 show some entries, which are presumed to be due to noise. Inaddition, some durations like 4 and 6, indicated by arrow 880, have nooccurrences. This may be a result of the time durations having discreteenough values for this example or, equivalently, the bins of the barchart time durations being wide enough.

As seen above, in some embodiments the ECG signal is sensed in samples,and the time durations are measured in numbers of samples. Again, if thebins of the bar chart are wide enough, they can produce a bar chart likebar chart 806, which is easy to work with even by having empty bins.

In some embodiments, from the measured durations, a representativeduration can be identified that best meets a plausibility criterion.Such a plausibility criterion can be implemented in a number of ways.For example, as seen above, the plausibility criterion may include thatthe representative duration is the one that occurs the most often amongthe measured durations. Additional ways are described later in thisdocument. In such embodiments, a heart rate of the patient can becomputed from a duration indicated by the representative duration. Thenit can be determined from the computed heart rate whether or not a shockcriterion is met. Discharge circuit 255 can be controlled, responsive tothe shock criterion being met, to discharge the stored electrical chargethrough patient 82 while support structure 170 is worn by patient 82, soas to deliver a shock to patient 82.

In embodiments, it is desired to add to these measurements' durations oftime intervals from additional channels. For example, in someembodiments the electrodes are further configured to sense another ECGsignal, and the processor is further configured to: detect other peaksoccurring sequentially within the sensed other ECG signal, establishother pairs of the detected other peaks, at least one of the other pairsbeing established by other peaks not occurring sequentially within thesensed other ECG signal, and measure other durations of time intervalsdefined by the established other pairs. In such embodiments, therepresentative duration can be identified from both the measureddurations and the measured other durations, thus providing more datapoints. Examples are now described.

FIG. 9 is a bar chart 906. Its horizontal axis 902 shows possible valuesfor the measured durations of time intervals. These values are innumbers of samples, for example as seen in axis 608 above. The verticalaxis 904 of bar chart 906 shows numbers for how often a measuredinterval had the duration of horizontal axis 902. Intervals in thisdataset range from 75-1000 samples, which could give a heart rateanywhere from 30-400 bpm (beats per minute). It will be observed thatthe most frequent occurrence is 3 for bar 981, which occurs at a valuebetween 300 and 350, perhaps at 335 samples.

In some embodiments the heart rate can be computed from therepresentative duration. For example, if at FIG. 9 the representativeduration is taken to be at 335 samples, the heart rate can be computedfrom that value, factoring in also the frequency with which the ECGsignal is sampled.

In FIG. 9 it will be observed that the durations are measured in samplesmuch more discretely than in FIG. 8 , and so there are very few timeswhen there is an occurrence of more than 1. To overcome this, in someembodiments processor 230 is further configured to discern clusters ofthe measured durations. In such embodiments, the representative durationis identified from the cluster that best meets a plausibility criterion.An example is now described.

FIG. 10 repeats bar chart 906 of FIG. 9 . In addition, FIG. 10 adds acomputed line 1007 that identifies clusters of the bar charts, accordingto grouping of the values of the horizontal axis 902. Line 1007 shows acluster with a maximum at point 1081, which corresponds to 331 samples.Line 1007 also shows clusters at a second harmonic 1082 (662 samples),and at a third harmonic 1083 (993 samples). As such, the cluster thatbest meets a plausibility criterion is at point 1081. Accordingly, therepresentative duration is identified at 331 samples, and as occurringabout 7 times after the grouping. This representative durationcorresponds to a heart rate of 90.6 bpm, which seems plausible.

While the chosen heart rate is 331 samples, it is possible that therewas no duration measured with that exact value. It is further possiblethat the chosen heart rate does not correspond with the heart ratecalculated for any given channel, which may raise questions. A WCDsystem incorporating this method may also have logic for deciding whento use the heart rate mode and when to use a simpler method. The modetends to be beneficial when there is a substantial disagreement in theheart rate between channels and there is not an obvious reason fordisqualifying one or more channels (like a dislodged ECG lead).

In some embodiments, the clusters are identified by filtering themeasured durations. For example, in such embodiments, computed line 1007can be generated by running a grouping kernel to identify the true R-Rinterval. Discreet time, digital implementations are preferred. Thegrouping kernel can be implemented as a boxcar Finite Impulse Response(FIR) filter with numerator coefficients of 1. This, effectively, countsup the intervals that are within the filter length. In addition, astandard FIR filter can be run, possibly in both directions, to smooththe result. This method is particularly attractive in a multichannelsystem because it is helpful to have numerically enough R-R intervals towork with. In a single channel system, the mode may still stand out, butit may not stand out as much because there are fewer intervalsaltogether. Other methods of identifying clusters (or groups) mayproduce similar results.

In some embodiments, the plausibility criterion includes that a fractionof the identified representative duration occurs less often than anoccurrence threshold. That fraction could be a half-, a third-, aquarter-harmonic and so on. For example, while the representativeduration has a value of D and occurs M times, the plausibility criterionmay include that a duration having a value of D/N occurs less often thanM/N times, where N takes one of the values of 2, 3, 4 and 5. This helpsmitigate against the possibility that an interval that is 2× the trueinterval may show up with the highest count, which can cause the heartrate to read half the actual value. If the patient's rhythm isnon-shockable, then there is not much harm in this, but if the patienthas a shockable rhythm, then such undercounting might cause a falseno-shock decision. An example is now described.

FIG. 11 is a bar chart 1106. Its horizontal axis 1102 shows possiblevalues for the measured durations of time intervals, in numbers ofsamples. Its vertical axis 1104 shows numbers for how often a measuredinterval had the duration of horizontal axis 1102.

In addition, FIG. 11 adds a computed line 1107 that identifies clustersof the bar charts, according to grouping. Line 1107 shows a cluster witha maximum at point 1181, which corresponds to 98 samples, and occurs13.57 times. Line 1107 also shows clusters at a second harmonic 1182, ata third harmonic 1183, at a fourth harmonic 1184, and at a fifthharmonic 1185.

It should be noted that the highest occurrence is at peak 1182. However,the half-harmonic of peak 1182 would be peak 1181, which does not occurless often than an occurrence threshold.

More particularly, in this example, the peak R-R interval would be atpeak 1182, which occurs M=16 times, and is at 194 samples. The moreadvanced plausibility criterion included that a duration having a valueof D/N, i.e. 194/2=97 samples occur less often than 16/2=8 times. Here,however, peak 1181 occurs 13.57 times at 98 samples, which is more than8, and therefore peak 1182 is rejected as the representative duration.Accordingly, another representative duration is considered, which couldbe ½ or ⅓ the peak R-R interval. Here, peak 1181 is chosen, which passesthe advanced plausibility criterion, even though it is shorter.

The devices and/or systems mentioned in this document perform functions,processes and/or methods. These functions, processes and/or methods maybe implemented by one or more devices that include logic circuitry. Sucha device can be alternately called a computer, and so on. It may be astandalone device or computer, such as a general purpose computer, orpart of a device that has one or more additional functions. The logiccircuitry may include a processor and non-transitory computer-readablestorage media, such as memories, of the type described elsewhere in thisdocument. Often, for the sake of convenience only, it is preferred toimplement and describe a program as various interconnected distinctsoftware modules or features. These, along with data are individuallyand also collectively known as software. In some instances, software iscombined with hardware, in a mix called firmware.

Moreover, methods and algorithms are described below. These methods andalgorithms are not necessarily inherently associated with any particularlogic device or other apparatus. Rather, they are advantageouslyimplemented by programs for use by a computing machine, such as ageneral-purpose computer, a special purpose computer, a microprocessor,a processor such as described elsewhere in this document, and so on.

This detailed description includes flowcharts, display images,algorithms, and symbolic representations of program operations within atleast one computer readable medium. An economy is achieved in that asingle set of flowcharts is used to describe both programs, and alsomethods. So, while flowcharts described methods in terms of boxes, theyalso concurrently describe programs.

Methods are now described.

FIG. 12 shows a flowchart 1200 for describing methods according toembodiments. According to an operation 1210, a first ECG signal of thepatient may be sensed, such as ECG signal 317. Sensing can be by theelectrodes.

According to another operation 1220, peaks occurring sequentially withinthe first ECG signal may be detected.

According to another operation 1230, pairs of the detected peaks may beestablished. At least one of the pairs may be established by peaks notoccurring sequentially.

According to another operation 1240, durations of time intervals definedby the established pairs may be measured.

According to another operation 1250, a representative duration may beidentified, which best meets a plausibility criterion. Therepresentative duration may be identified from the measured durations.

According to another operation 1260, a heart rate of the patient may becomputed. Computing may be from a duration indicated by therepresentative duration. According to another operation 1261, thecomputed heart rate of the patient may be stored in a memory. Computingmay be from a duration indicated by the representative duration.According to another, optional operation 1262, the computed heart ratemay be transmitted wirelessly, for example by a communication module.

According to another, optional operation 1264, the computed heart ratemay be displayed on a screen.

According to an operation 1268, a second ECG signal of the patient maybe sensed, such as ECG signal 318. According to one more operation 1270,it may be determined whether or not a shock criterion is met. Thedetermination may be from the second ECG signal of operation 1268. If atoperation 1270 the answer is “no”, indicated by a cross-out, thenexecution may return to a previous operation, such as operation 1210.

If at operation 1270 the answer is “yes”, indicated by a checkmark, thenaccording to another operation 1280, responsive to the shock criterionbeing met the discharge circuit may be controlled to discharge thestored electrical charge through the patient. Discharging may be whilethe support structure is worn by the ambulatory patient, so as todeliver a shock to the patient.

In the methods described above, each operation can be performed as anaffirmative step of doing, or causing to happen, what is written thatcan take place. Such doing or causing to happen can be by the wholesystem or device, or just one or more components of it. It will berecognized that the methods and the operations may be implemented in anumber of ways, including using systems, devices and implementationsdescribed above. In addition, the order of operations is not constrainedto what is shown, and different orders may be possible according todifferent embodiments. Examples of such alternate orderings may includeoverlapping, interleaved, interrupted, reordered, incremental,preparatory, supplemental, simultaneous, reverse, or other variantorderings, unless context dictates otherwise. Moreover, in certainembodiments, new operations may be added, or individual operations maybe modified or deleted. The added operations can be, for example, fromwhat is mentioned while primarily describing a different system,apparatus, device or method.

A person skilled in the art will be able to practice the presentinvention in view of this description, which is to be taken as a whole.Details have been included to provide a thorough understanding. In otherinstances, well-known aspects have not been described, in order to notobscure unnecessarily this description.

This description includes one or more examples, but this fact does notlimit how the invention may be practiced. Indeed, examples, instances,versions or embodiments of the invention may be practiced according towhat is described, or yet differently, and also in conjunction withother present or future technologies. Other such embodiments includecombinations and sub-combinations of features described herein,including for example, embodiments that are equivalent to the following:providing or applying a feature in a different order than in a describedembodiment; extracting an individual feature from one embodiment andinserting such feature into another embodiment; removing one or morefeatures from an embodiment; or both removing a feature from anembodiment and adding a feature extracted from another embodiment, whileproviding the features incorporated in such combinations andsub-combinations.

In general, the present disclosure reflects preferred embodiments of theinvention. The attentive reader will note, however, that some aspects ofthe disclosed embodiments extend beyond the scope of the claims. To therespect that the disclosed embodiments indeed extend beyond the scope ofthe claims, the disclosed embodiments are to be considered supplementarybackground information and do not constitute definitions of the claimedinvention.

In this document, the phrases “constructed to” and/or “configured to”denote one or more actual states of construction and/or configurationthat is fundamentally tied to physical characteristics of the element orfeature preceding these phrases and, as such, reach well beyond merelydescribing an intended use. Any such elements or features can beimplemented in a number of ways, as will be apparent to a person skilledin the art after reviewing the present disclosure, beyond any examplesshown in this document.

Any and all parent, grandparent, great-grandparent, etc. patentapplications, whether mentioned in this document or in an ApplicationData Sheet (“ADS”) of this patent application, are hereby incorporatedby reference herein as originally disclosed, including any priorityclaims made in those applications and any material incorporated byreference, to the extent such subject matter is not inconsistentherewith.

In this description a single reference numeral may be used consistentlyto denote a single item, aspect, component, or process. Moreover, afurther effort may have been made in the drafting of this description touse similar though not identical reference numerals to denote otherversions or embodiments of an item, aspect, component or process thatare identical or at least similar or related. Where made, such a furthereffort was not required, but was nevertheless made gratuitously so as toaccelerate comprehension by the reader. Even where made in thisdocument, such a further effort might not have been made completelyconsistently for all of the versions or embodiments that are madepossible by this description. Accordingly, the description controls indefining an item, aspect, component, or process, rather than itsreference numeral. Any similarity in reference numerals may be used toinfer a similarity in the text, but not to confuse aspects where thetext or other context indicates otherwise.

The claims of this document define certain combinations andsubcombinations of elements, features and steps or operations, which areregarded as novel and non-obvious. Additional claims for other suchcombinations and subcombinations may be presented in this or a relateddocument. These claims are intended to encompass within their scope allchanges and modifications that are within the true spirit and scope ofthe subject matter described herein. The terms used herein, including inthe claims, are generally intended as “open” terms. For example, theterm “including” should be interpreted as “including but not limitedto,” the term “having” should be interpreted as “having at least,” etc.If a specific number is ascribed to a claim recitation, this number is aminimum but not a maximum unless stated otherwise. For example, where aclaim recites “a” component or “an” item, it means that it can have oneor more of this component or item.

1-14. (canceled)
 15. A wearable cardioverter defibrillator (WCD) system,comprising: a support structure configured to be worn by a patient; anenergy storage module configured to store an electrical charge; adischarge circuit coupled to the energy storage module; a plurality ofelectrodes configured to be coupled with the patient's body; a processorconfigured to: sense, with the plurality of electrodes, a firstElectrocardiogram (ECG) signal of the patient in a first channel, and asecond ECG signal of the patient in a second channel; identify a firstgroup of peaks in the first ECG signal; measure intervals between afirst number of peaks in the first group of peaks to provide a first setof intervals from the first channel; identify a second group of peaks inthe second ECG signal; measure intervals between a second number ofpeaks in the second group of peaks to provide a second set of intervalsfrom the second channel; combine the first set of intervals from thefirst channel with the second set of intervals from the second channelto provide a combined group of intervals; identify a representativeinterval in the combined group of intervals corresponding to a mode ofthe combined group of intervals; compute a heart rate value for thepatient from the representative interval; determine based at least inpart on the heart rate value whether one or more shock criteria are met;and control, responsive to the one or more shock criteria being met, thedischarge circuit to discharge the stored electrical charge through thepatient while the support structure is worn by the patient to deliver atherapeutic shock to the patient.
 16. The WCD system of claim 15,further comprising: a communication module configured to wirelesslytransmit the heart rate to a remote device.
 17. The WCD system of claim15, further comprising: a user interface configured to display the heartrate.
 18. The WCD system of claim 15, wherein: the measured intervals inthe first group of peaks and the second group of peaks includeconsecutive intervals and non-consecutive intervals.
 19. The WCD systemof claim 15, wherein: the first number of peaks comprises all of thepeaks in the first group of peaks; and the second number of peakscomprises all of the peaks in the second group of peaks.
 20. The WCDsystem of claim 15, wherein: all of the intervals in the first group ofpeaks are measured; and all of the intervals in the second group ofpeaks are measured.
 21. The WCD of claim 15, wherein the processor isfurther configured to: discern clusters of intervals in the combinedgroup of intervals; wherein the representative interval is determinedfrom a cluster that corresponds to the mode of the combined group ofintervals.
 22. The WCD of claim 21, wherein: the clusters are discernedby filtering intervals in the combined group of intervals to identifythe representative interval for the cluster.
 23. The WCD of claim 21,wherein: the clusters are discerned by running a grouping kernel on theintervals in the combined group of intervals identify the representativeinterval for the cluster.
 24. The WCD of claim 23, wherein: the groupingkernel is implemented as a boxcar Finite Impulse Response (FIR) filter.25-34. (canceled)
 35. A method for a cardiac monitoring device, thecardiac monitoring device including a processor, a memory, andelectrodes, the method comprising: sensing, by the electrodes, anElectrocardiogram (ECG) signal of a patient; detecting, with theprocessor, peaks occurring within the ECG signal; establishing pairs ofthe detected peaks with the processor, at least one of the pairs beingestablished by peaks not occurring sequentially; measuring, with theprocessor, durations of time intervals defined by the established pairsof the detected peaks; identifying, with the processor and from themeasured durations of time intervals, a representative duration, whereinthe representative duration comprises a most common value of themeasured durations of time intervals; computing a heart rate of thepatient, with the processor, from the representative duration; storing,from the processor, the heart rate in the memory; determining, with theprocessor and from the heart rate, whether an arrhythmia event isdetected; and generating a notification regarding patient statusresponsive to the detected arrhythmia event.
 36. The method of claim 35,wherein: cardiac monitoring device further includes a communicationmodule; and further comprising wirelessly transmitting the stored heartrate.
 37. The method of claim 35, wherein: cardiac monitoring devicefurther includes a screen; and further comprising displaying the storedheart rate on the screen.
 38. The method of claim 35, furthercomprising: establishing all possible pairs of the detected peaks. 39.The method of claim 35, further comprising: sensing, by the electrodes,another ECG signal of the patient distinct from the ECG signal;detecting, with the processor, other peaks occurring within the otherECG signal; establishing, with the processor, other pairs of thedetected other peaks, at least one of the other pairs being establishedby other peaks not occurring sequentially within the other ECG signal;measuring, with the processor, other durations of time intervals definedby the established other pairs; and identifying, with the processor, therepresentative duration from both the measured durations of timeintervals and the measured other durations.
 40. The method of claim 35,wherein: the most common value comprises a mode of the measureddurations of time intervals.
 41. The method of claim 35, wherein: afraction of the representative duration occurs less often than anoccurrence threshold.
 42. The method of claim 35, wherein: therepresentative duration has a value of D and occurs M times; and aduration having a value of D/N, where N takes one of the values of 2, 3,4 and 5, occurs less often than M/N times.
 43. The method of claim 35,wherein: the heart rate is computed from a duration having a number ofoccurrences that is one-half or one-third of a number of occurrence ofthe representative duration.
 44. The method of claim 35, wherein: thecardiac monitoring device includes a support structure configured to beworn by the patient, an energy storage module storing an electricalcharge, and a discharge circuit coupled to the energy storage module,the method further comprising: responsive to the detected arrhythmiaevent, controlling, with the processor and responsive to a shockcriterion being met, the discharge circuit to discharge the storedelectrical charge through the patient while the support structure isworn by the patient to deliver a shock to the patient.